<template>
  <div v-if="total">
    <div class="todo-footer">
      <label>
        <!-- methods方法实现 -->
        <!-- <input type="checkbox" :checked="isAll" @change="checkAll"/> -->

        <!-- v-model实现 -->
        <input type="checkbox" v-model="isAll"/>
      </label>
      <span>
        <span>已完成{{doneTotsl}}</span> / 全部{{total}}
      </span>
      <button class="btn btn-danger" @click="clearAll">清除已完成任务</button>
    </div>
  </div>
</template>

<script>
export default {
  name:'TodoHeader',
  props:['todos','checkAllTodo','clearAllTodo'],
  computed:{
    total(){
      return this.todos.length
    },
    // isAll(){
    //   return this.total=== this.doneTotsl && this.total > 0 
    // },
    isAll:{
      get(){
        return this.total=== this.doneTotsl && this.total > 0 
      },
      set(value){
        this.checkAllTodo(value)
      }
    },
    doneTotsl(){
      //使用filter实现
      // return this.todos.filter(todo=>todo.done).length

      //使用reduce实现
      return this.todos.reduce((pre,todo)=> pre += (todo.done ? 1 : 0),0)
    }
  },
  methods:{
    // checkAll(e){
    //   this.checkAllTodo(e.target.checked)
    // },
    clearAll(){
      this.clearAllTodo()
    }
  }
}
</script>

<style scoped>
  /*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>